Method and a system for adjusting nozzle area in steam turbines

ABSTRACT

The various embodiments herein provide a method and a system for controlling a nozzle area in a steam turbine. The system comprises a nozzle ring provided with a plurality of nozzle blades at an outer edge. The steam enters into the nozzle ring and jets out on the blades of the rotor disk. When there is an off design condition, the nozzle blades are plugged or opened by adding or removing the inserts. The nozzle area is increased or decreased by opening or plugging the nozzle passages manually or automatically with the help of the inserts. The embodiments herein provide a cost effective and simple solution to deal with the off design conditions.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority of the Indian Provisional Patent application with serial number 4240/CHE/2012 filed at Indian Patent Office on Oct. 11, 2012 with title, “A Method and a System for Adjusting Nozzle Area in Steam Turbines” and the contents of which is incorporated in entirety.

BACKGROUND

1. Technical Field

The embodiments herein generally relate to steam turbines and particularly relates to a method for adjusting a nozzle area in a steam turbine. The embodiments herein more particularly relates to a method and a system for controlling the area of a nozzle of a steam turbine under the “off-design” operating conditions.

2. Description of the Related Art

The turbines are rotating machines which convert the energy contained in a working fluid to a useful work. In general, a turbine comprises a shaft and a circular disk or a ring. The outer circumference of the circular disk comprises a series of blades. The series of blades are shaped and aligned based on a rotational speed of the turbine, energy in the fluid and an application. There are numerous types of turbines depending on a type of an input, such as steam, water, wind, gas, etc.

The steam turbines, especially used in the cogeneration systems, cater to an industry using the steam as a process fluid for the heating and cooling purposes. In the process industries, such as distilleries, paper mills etc., a demand for the steam depends on a production capacity of a particular product. The variations in a flow of a driving fluid to the steam turbines are caused due to a variety of reasons like the steam availability, the load variations, and the process requirements amongst others. The different volumes/loads of the steam are required for the different applications. In most of the cases, these variations last for several weeks or months. A performance of a turbine is a function of an inlet flow of the driving fluid. A reduction in the inlet flow of the driving fluid results in a drastic drop in a performance of the turbine. The drop in the turbine performance is due to an area of a nozzle ring. The area of the nozzle ring designed for a specific value of flow experiences an ‘off design’ condition at the lower or higher flow rates.

The turbines are very sensitive to a design condition and the turbines work properly when operated at the rated parameters such as a temperature, a pressure, an amount of steam, etc. The size and shape of the turbine blades are also designed to function at the specific conditions. The performance of a steam turbine deteriorates under the off design conditions. The off design conditions corresponds to a change in a pressure, a temperature, a flow of driving fluid etc. The biggest challenge in a cogeneration system is to deal with the off design conditions by the steam turbines.

For solving the issues raised by the off design conditions, the turbine manufacturers have adopted a method or arrangement called as “Partial admission turbines”. In a Partial admission turbine, the nozzle ring is spilt into a plurality (generally four to five) of “arcs”. When there is a flow variation in the driving fluid, one of the arcs is closed. Thus the nozzle ring is not completely opened but is partially opened. Though there can be a slight performance offset due to the windage flows, it results in taller and more practical nozzles.

It is also common practice to have several ‘arcs’ in the ‘steam chests’. A fluid flow is controlled by the individual control valves. This method of throttling the steam has assumed a widespread practice as this method preserves the design conditions in the nozzles in each steam chest. However this requires a multiplicity of valves. When the turbines are required to operate for long durations at the off-design conditions, a simpler apparatus would be more desirable from the perspective of a cost and simplicity of an installation.

Hence there is need for a system and a method to control a nozzle area for passing a driving fluid efficiently under the off design conditions in a steam turbine.

The abovementioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.

OBJECTS OF THE EMBODIMENTS

The primary object of the embodiments herein is to provide a method and a system to provide a simple and a cost effective solution for controlling a nozzle area of a steam turbine.

Another object of the embodiments herein is to provide a method and a system for controlling a steam inlet into a steam turbine under the off design conditions.

Yet another object of the embodiments herein is to provide a method and system for plugging inserts into or removing from the nozzle blades, depending on a demand or a flow of the driving fluid.

Yet another object of the embodiments herein is to provide a nozzle tuning sheet for determining number of nozzle passages to be blocked.

Yet another object of the embodiments herein is to provide a method and a system for controlling the nozzle area of full-admission turbines.

These and other objects and advantages of the embodiments herein will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

SUMMARY

The various embodiments herein provide a system and method for adjusting a nozzle area in a steam turbine. The system comprises a nozzle ring, a plurality of nozzle blades provided in the nozzle ring and an insert to block a nozzle passage formed between two adjacent nozzle blades in the plurality of nozzle blades. The insert blocks the nozzle passages to control a flow of a driving fluid during an off-design condition.

According to an embodiment herein, the nozzle passages are plugged by the inserts manually to decrease a nozzle area.

According to an embodiment herein, the nozzle passages are plugged by the inserts manually to decrease a nozzle area in a full admission turbine or in a partial admission turbine.

According to an embodiment herein, the inserts are removed from the nozzle passages manually to increase a nozzle area.

According to an embodiment herein, the inserts are removed from the nozzle passages manually to increase a nozzle area in a full admission turbine or in a partial admission turbine.

According to an embodiment herein, a number of nozzle passages are blocked by inserting the inserts based on a demand of the driving fluid in an off-design condition, and wherein a reduction or a variation in a demand of a driving fluid is caused in the off-design condition.

According to an embodiment herein, the inserts are provided with a socket head screw to hold the inserts to the nozzle ring.

According to an embodiment herein, the inserts are designed to fit with a contour of the nozzle passage.

According to an embodiment herein, the insert is made up of stainless steel.

According to an embodiment herein, the driving fluid is steam.

According to an embodiment herein, the nozzle ring is aligned behind a turbine rotor disk.

According to an embodiment herein, the nozzle ring is bolted to an inlet manifold of a turbine assembly.

According to an embodiment herein, the nozzle blades are provided at an outer edge of the nozzle ring.

According to an embodiment herein, the nozzle blades are made up of stainless steel.

According to an embodiment herein a method is provided for controlling a driving fluid in turbine during off-design condition. The method comprises the steps of mounting and aligning a nozzle ring behind a turbine rotor disk, selecting a number of nozzle passages to be blocked in the nozzle ring and blocking the selected number of nozzle rings by inserting an insert into a respective nozzle passage. The selected numbers of nozzle passages are blocked by the inserts to control a flow of a driving fluid based on a demand in an off-design condition. A number of nozzle passages are blocked by inserting the inserts based on a demand of the driving fluid in an off-design condition, and wherein a reduction or a variation in a demand of a driving fluid is caused in the off-design condition.

According to an embodiment herein, the nozzle passages are plugged by the inserts manually to decrease a nozzle area.

According to an embodiment herein, the nozzle passages are plugged by the inserts manually to decrease a nozzle area in a full admission turbine or in a partial admission turbine.

According to an embodiment herein, the inserts are removed from the nozzle passages manually to increase a nozzle area.

According to an embodiment herein, the inserts are removed from the nozzle passages manually to increase a nozzle area in a full admission turbine or in a partial admission turbine.

According to an embodiment herein, the inserts are provided with a socket head screw to hold the inserts to the nozzle ring.

According to an embodiment herein, the inserts are designed to fit with a contour of the nozzle passage.

According to an embodiment herein, the nozzle ring is bolted to an inlet manifold of a turbine assembly.

According to an embodiment herein, the insert is made up of stainless steel.

According to an embodiment herein, the driving fluid is steam.

The various embodiments herein provide a method and a system for adjusting a nozzle area of a steam turbine. The system comprises a nozzle ring. The nozzle ring comprises a plurality of nozzle blades fixed on the outer circumference of the nozzle ring. The steam enters into the nozzle ring and jets out on the blades of the rotor disk. When an off design condition is foreseen, the nozzle passages are plugged by a blocking means called the “inserts”. The nozzle area is increased or decreased by opening or plugging the nozzle passages manually with the help of the inserts.

According to an embodiment herein, a system for controlling the nozzle area of a steam turbine is provided. The system comprises a nozzle ring aligned behind a turbine rotor disk. The nozzle ring is provided with a plurality of nozzle blades. The nozzle blades are made up of stainless steel. The nozzle ring is bolted to an inlet manifold of the steam turbine assembly. The system further comprises a blocking means called an insert. The insert is plugged between the nozzle blades to block a driving fluid passageway under the off design operating conditions. The insert is made up of stainless steel and higher grade steel is used based on the requirements of the driving fluid.

According to an embodiment herein, a method for controlling an inlet of a driving fluid is provided. The method comprises, predicting or foreseeing a large change in a demand or a production and adjusting or varying a flow of the driving fluid through a steam turbine accordingly by blocking the nozzle passages between the nozzle blades manually by plugging the passages in a predetermined pattern to obtain a required nozzle area.

According to an embodiment herein, a chart for operating a steam turbine under the off design condition is generated and provided. The chart directs a user of the steam turbine to plug a required number of inserts in a space between the nozzle blades. Based on a demand/flow of the driving fluid, a predetermined pattern of plugging the nozzle gap is provided

These and other objects and advantages of the embodiments herein will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:

FIG. 1 illustrates a partial cross sectional view of a rotor disk for a single stage steam turbine with an insert plugged between the nozzle blades, according to an embodiment herein.

FIG. 2 illustrates a partial isometric view of the nozzle blades in a nozzle ring with an insert plugged between any two nozzle blades, according to an embodiment herein.

FIG. 3 illustrates a top view of the nozzle ring without inserts, according to an embodiment herein.

FIG. 4 illustrates a top view of the nozzle ring with an insert, according to an embodiment herein.

FIG. 5 illustrates a front view of the nozzle ring without inserts, according to an embodiment herein.

FIG. 6 illustrates a front view of the nozzle ring with inserts, according to an embodiment herein.

FIG. 7 illustrates a front view of an insert, according to an embodiment herein.

FIG. 8 illustrates a top view of an insert, according to an embodiment herein.

FIG. 9 illustrates a nozzle tuning sheet for determining number of nozzle passages to be blocked, according to an embodiment herein.

Although the specific features of the embodiments herein are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the embodiments herein.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following detailed description, a reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.

The various embodiments herein provide a system and method for adjusting a nozzle area in a steam turbine. The system comprises a nozzle ring, a plurality of nozzle blades provided in the nozzle ring and an insert to block a nozzle passage formed between two adjacent nozzle blades in the plurality of nozzle blades. The insert blocks the nozzle passages to control a flow of a driving fluid during an off-design condition.

According to an embodiment herein, the nozzle passages are plugged by the inserts manually to decrease a nozzle area.

According to an embodiment herein, the nozzle passages are plugged by the inserts manually to decrease a nozzle area in a full admission turbine or in a partial admission turbine.

According to an embodiment herein, the inserts are removed from the nozzle passages manually to increase a nozzle area.

According to an embodiment herein, the inserts are removed from the nozzle passages manually to increase a nozzle area in a full admission turbine or in a partial admission turbine.

According to an embodiment herein, a number of nozzle passages are blocked by inserting the inserts based on a demand of the driving fluid in an off-design condition, and wherein a reduction or a variation in a demand of a driving fluid is caused in the off-design condition.

According to an embodiment herein, the inserts are provided with a socket head screw head to hold the inserts to the nozzle ring.

According to an embodiment herein, the inserts are designed to fit with a contour of the nozzle passage.

According to an embodiment herein, the insert is made up of stainless steel.

According to an embodiment herein, the driving fluid is steam.

According to an embodiment herein, the nozzle ring is aligned behind a turbine rotor disk.

According to an embodiment herein, the nozzle ring is bolted to an inlet manifold of a turbine assembly.

According to an embodiment herein, the nozzle blades are provided at an outer edge of the nozzle ring.

According to an embodiment herein, the nozzle blades are made up of stainless steel.

According to an embodiment herein a method is provided for controlling a driving fluid in turbine during off-design condition. The method comprises the steps of mounting and aligning a nozzle ring behind a turbine rotor disk, selecting a number of nozzle passages to be blocked in the nozzle ring and blocking the selected number of nozzle rings by inserting an insert into a respective nozzle passage. The selected numbers of nozzle passages are blocked by the inserts to control a flow of a driving fluid based on a demand in an off-design condition. A number of nozzle passages are blocked by inserting the inserts based on a demand of the driving fluid in an off-design condition, and wherein a reduction or a variation in a demand of a driving fluid is caused in the off-design condition.

According to an embodiment herein, the nozzle passages are plugged by the inserts manually to decrease a nozzle area.

According to an embodiment herein, the nozzle passages are plugged by the inserts manually to decrease a nozzle area in a full admission turbine or in a partial admission turbine.

According to an embodiment herein, the inserts are removed from the nozzle passages manually to increase a nozzle area.

According to an embodiment herein, the inserts are removed from the nozzle passages manually to increase a nozzle area in a full admission turbine or in a partial admission turbine.

According to an embodiment herein, the inserts are provided with a socket head type screw head to hold the inserts to the nozzle ring.

According to an embodiment herein, the inserts are designed to fit with a contour of the nozzle passage.

According to an embodiment herein, the nozzle ring is bolted to an inlet manifold of a turbine assembly.

According to an embodiment herein, the insert is made up of stainless steel.

According to an embodiment herein, the driving fluid is steam.

The various embodiments herein provide a method and a system for controlling a nozzle area of a steam turbine to account for the off-design conditions. The system comprises a nozzle ring. The nozzle ring comprises a plurality of nozzle blades fixed on the outer circumference of the nozzle ring. The steam enters into the nozzle ring and jets out on the blades of the rotor disk. When there is an off design condition, the nozzle blades are plugged by a blocking means called the “inserts”. The nozzle area is increased or decreased by opening or plugging the nozzle passages manually with the help of the inserts.

According to an embodiment herein, a system for controlling an inlet of the driving fluid is provided. The system comprises a nozzle ring aligned behind a turbine rotor disk. The nozzle ring is provided with a plurality of nozzle blades at an edge surface. The nozzle blades are made up of stainless steel. The nozzle ring is bolted to an inlet manifold of the steam turbine assembly. The system further comprises a blocking means called an insert. The insert is plugged between the nozzle blades to block a driving fluid passageway under the off design operating conditions. The insert is made up of stainless steel or higher grade steel based on the requirements of the driving fluid.

According to an embodiment herein, a method for controlling the inlet of the driving fluid is provided. The method comprises, predicting or foreseeing a large change in a demand or a production and adjusting or varying a flow of the driving fluid through the steam turbine accordingly by blocking the gaps between the nozzle blades manually by plugging the inserts in a predetermined pattern in the gaps to obtain a required area for the nozzle.

According to an embodiment herein, a method for adding inserts between the nozzle blades is provided. The inserts are plugged between the nozzle blades to block a driving fluid passageway under the off design operating conditions. The method for adding inserts comprises the steps of: removing an inlet casing by removing the bolts, removing nozzle ring from the inlet casing by removing bolts, determining number of nozzle passages to be blocked by referring to nozzle tuning sheet, bolting inserts onto the nozzle ring to block the requisite number of passages, bolting nozzle ring back to the inlet casing and the inlet casing is then bolted back to the turbine and the machine is ready for operation.

According to an embodiment herein, a nozzle tuning sheet for operating a steam turbine under the off design condition is generated and provided. The nozzle tuning sheet directs a user of the steam turbine to plug a required number of inserts in a space between the nozzle blades. Based on a demand/flow of the driving fluid, a predetermined pattern of plugging the nozzle gap is provided.

FIG. 1 illustrates a partial cross sectional view of a rotor disk for a single stage steam turbine with an insert plugged between the nozzle blades, according to an embodiment herein. With respect to FIG. 1, the steam turbine assembly is covered with an inlet casing 101. The covered side of the inlet casing 101 is bolted to the steam turbine assembly and the opposite side of the inlet casing 101 is connected to the pipes for supplying a driving fluid to the turbine rotor disk 104. A plurality of blades 107 is arranged over the peripheral edges of the rotor disk 104 of the steam turbine. The blade arrangement 107 is designed based on the specific conditions and the suitable requirements. A nozzle ring 103 is fixed directly behind the blade arrangement 107. The nozzle ring 103 is fixed to the inlet casing through a plurality bolts and is aligned with the blade arrangement 107. The outer edge of the nozzle ring 103 comprises a plurality of nozzle blades 106. The nozzle blade 106 receives the driving fluid as input and produces a jet of high speed driving fluid as output. The nozzle blade 106 is designed to withstand the different temperature and pressure conditions. In case of a reduction in a demand of the driving fluid, the performance of the steam turbine drops considerably. The reduction or variation in the demand of the driving fluid is termed as an off design condition. The performance of the steam turbine under the off design condition is improved by controlling the nozzle passage area. The nozzle passage area is controlled by blocking or opening the predetermined the nozzle passages with a plugging means. The plugging means are termed as the inserts 102. The inserts 102 are plugged into the space between any two successive nozzle blades 106 through a socked head screw 105. The inserts 102 block the flow of the driving fluid onto the rotor disk 104. Depending on a demand or a flow of the driving fluid, the inserts 102 are plugged into or removed from the nozzle blades 106. Bolt holes 108 are provided on the nozzle ring for clamping the nozzle to the inlet manifold.

FIG. 2 illustrates a partial isometric view of the nozzle blades in a nozzle ring with an insert plugged between any two nozzle blades, according to an embodiment herein. With respect to FIG. 2, three nozzle blades 106 a, 106 b and 106 c out of the plurality of nozzle blades are shown. The nozzle blades 106 a, 106 b and 106 c control a supply or a flow of a driving fluid. The driving fluid experiences a large area at the input between the nozzle blades 106 a and 106 b. The nozzle blades 106 a and 106 b are designed in such a way that, it provides a large cross sectional area at the input and a small cross sectional area at the output as shown in FIG. 2. After a supply of a driving fluid, the driving fluid flows through the passage between the nozzle blades 106 a and 106 b. The curved design of the nozzle blades 106 a and 106 b enables to direct the driving fluid towards the small cross sectional area. The small cross sectional area between the ends of the nozzle blades 106 a and 106 b produces a jet of the driving fluid at an output and directs the jet of the driving fluid on the blades of the steam turbine.

When there is a drop in a demand of driving fluid, a predetermined set of nozzle passages are blocked. With respect to FIG. 2, the gap between the nozzle blades 106 b and 106 c are blocked to maintain the characteristics of the jet of the driving fluid coming out of the nozzle passages. The gap between nozzle blades 106 b and 106 c are blocked by a plugging device called an insert 102. The insert 102 is plugged between any two successive nozzle blades 106 b and 106 c. The inserts 102 are designed to fit properly with the contours of the nozzle blades 106 b and 106 c. The inserts 102 are plugged between the nozzle blades 106 b and 106 c by a socket head screw 105. The socket head screw 105 is a socket head fastener which strongly holds the inserts 102 to the nozzle ring 103. The socket head screw 105 does not protrude out of the insert but instead provides a flushed joint. The inserts 102 block the nozzlepassage of the driving fluid. As a result the blocked driving fluid passes through the opened nozzle gaps such as gap between nozzle blades 106 a and 106 b.

FIG. 3 illustrates a top view of the nozzle ring without inserts, according to an embodiment herein. The outer edge of the nozzle ring comprises a plurality of nozzle blades 106 a and 106 b as shown in FIG. 3. The nozzle blades 106 a and 106 b receives the driving fluid as input and produces a jet of high speed driving fluid as output. The nozzle blades 106 a and 106 b are designed to withstand the different temperature and pressure conditions. In case of a reduction in a demand of the driving fluid, the performance of the steam turbine drops considerably. The gap between the nozzle blades 106 a and 106 b are blocked to maintain the characteristics of the jet of the driving fluid coming out of the nozzle passages. A tapped hole 301 is provided for clamping the insert with socket head bolts.

FIG. 4 illustrates a top view of the nozzle ring with an insert, according to an embodiment herein. The inserts 102 are plugged into the space i.e. through a tapped hole 301 between any two successive nozzle blades 106 a and 106 b using a socked head screw 105. The inserts 102 block the flow of the driving fluid onto the rotor disk. Depending on a demand or a flow of the driving fluid, the inserts 102 are plugged into or removed from the nozzle blades 106 a and 106 b.

FIG. 5 illustrates a front view of the nozzle ring without inserts, according to an embodiment herein. The inserts are plugged into the space i.e. using a tapped hole 301 between any two successive nozzle blades 106 (between 106 a and 106 b as shown in FIG. 4) and a socked head screw. Bolt holes 108 are provided for clamping the nozzle to the inlet manifold. The nozzle blades are indicated with phantom lines in FIG. 5.

FIG. 6 illustrates a front view of the nozzle ring with inserts, according to an embodiment herein. The inserts 102 are plugged into the space i.e. through a tapped hole 301 between any two successive nozzle blades 106 (between 106 a and 106 b as shown in FIG. 4) and through a socked head screw 105 and the nozzle is clamped to the inlet manifold through a bolt hole 108 as shown in FIG. 6. The nozzle blades are indicated with phantom lines in FIG. 6.

FIG. 7 illustrates a front view of an insert, according to an embodiment herein. The inserts 102 are used to block the flow of the driving fluid onto the rotor disk. Depending on a demand or a flow of the driving fluid, the inserts 102 are plugged into or removed from the nozzle blades. The inserts 102 are clamped using a socket head screw passed through a counter bored hole 701.

FIG. 8 illustrates a top view of an insert, according to an embodiment herein. The inserts 102 are clamped using a socket head screw passed through a counter bored hole 701. The profile of the counter bored hole is as shown in FIG. 8.

FIG. 9 illustrates a nozzle tuning sheet for determining number of nozzle passages to be blocked, according to an embodiment herein. The inserts are used to block the flow of the driving fluid onto the rotor disk. Depending on a demand or a flow of the driving fluid, the inserts are plugged into or removed from the nozzle blades. A nozzle tuning sheet as shown in FIG. 9 is referred for determining number of nozzle passages to be blocked.

The embodiments herein provide a method and a system for controlling the nozzle area in a steam turbine. The method and system offers a greater efficiency under the off design conditions. The method of the embodiments herein provides a feasibility of being adapted (retrofit) in the full admission turbines. The embodiments herein avoid a requirement of a steam chest and provide a cost effective solution. The embodiments herein provide a simpler apparatus from a perspective of cost and simplicity of installation. The embodiments herein provides a manually operated blocking means called inserts to control the inlet of driving fluid in different conditions. A chart is provided to the operating personnel, to assist in plugging the required number of inserts in between the nozzle blades for adjusting and controlling the steam inlet.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.

Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between. 

What is claimed is:
 1. A system for adjusting a nozzle area in a steam turbine comprising: a nozzle ring; a plurality of nozzle blades provided in the nozzle ring; and an insert to block a nozzle passage formed between two adjacent nozzle blades in the plurality of nozzle blades; wherein the insert block the nozzle passages to control a flow of a driving fluid during an off-design condition.
 2. The system according to claim 1, wherein the nozzle passages are plugged by the inserts manually to decrease a nozzle area, and wherein the nozzle passages are plugged by the inserts manually to decrease a nozzle area in a full admission turbine or in a partial admission turbine.
 3. The system according to claim 1, wherein the inserts are removed from the nozzle passages manually to increase a nozzle area, and wherein the inserts are removed from the nozzle passages manually to increase a nozzle area in a full admission turbine or in a partial admission turbine.
 4. The system according to claim 1, wherein a number of nozzle passages are blocked by inserting the inserts based on a demand of the driving fluid in an off-design condition, and wherein a reduction or a variation in a demand of a driving fluid is caused in the off-design condition.
 5. The system according to claim 1, wherein the inserts are provided with a socket head screw to hold the inserts to the nozzle ring.
 6. The system according to claim 1, wherein the inserts are designed to fit with a contour of the nozzle passage.
 7. The system according to claim 1, wherein the insert is made up of stainless steel.
 8. The system according to claim 1, wherein the driving fluid is steam.
 9. The system according to claim 1, wherein the nozzle ring is aligned behind a turbine rotor disk.
 10. The system according to claim 1, wherein the nozzle ring is bolted to an inlet manifold of a turbine assembly.
 11. The system according to claim 1, wherein the nozzle blades are provided at an outer edge of the nozzle ring.
 12. The system according to claim 1, wherein the nozzle blades are made up of stainless steel.
 13. A method of controlling driving fluid in turbine during off-design condition, the method comprises: mounting and aligning a nozzle ring behind a turbine rotor disk; selecting a number of nozzle passages to be blocked in the nozzle ring; and blocking the selected number of nozzle rings by clamping inserts into a the respective nozzle passages; wherein the selected number of nozzle passages are blocked by the inserts to control a flow of a driving fluid based on a demand in an off-design condition, and wherein a number of nozzle passages are blocked by inserting the inserts based on a demand of the driving fluid in an off-design condition, and wherein a reduction or a variation in a demand of a driving fluid is caused in the off-design condition.
 14. The method according to claim 13, wherein the nozzle passages are plugged by the inserts manually to decrease a nozzle area, and wherein the nozzle passages are plugged by the inserts manually to decrease a nozzle area in a full admission turbine or in a partial admission turbine.
 15. The method according to claim 13, wherein the inserts are removed from the nozzle passages manually to increase a nozzle area, and wherein the inserts are removed from the nozzle passages manually to increase a nozzle area in a full admission turbine or in a partial admission turbine
 16. The method according to claim 13, wherein the inserts are provided with a socket head type screw head to hold the inserts to the nozzle ring.
 17. The method according to claim 13, wherein the inserts are designed to fit with a contour of the nozzle passage.
 18. The method according to claim 13, wherein the nozzle ring is bolted to an inlet manifold of a turbine assembly.
 19. The method according to claim 13, wherein the insert is made up of stainless steel.
 20. The method according to claim 13, wherein the driving fluid is steam. 